U.S. patent application number 11/395569 was filed with the patent office on 2007-10-04 for imaging-based bar code reader utilizing stitching method and swipe guide.
This patent application is currently assigned to SYMBOL TECHNOLOGIES, INC.. Invention is credited to Edward Barkan, Miroslav Trajkovic, Igor R. Vinogradov.
Application Number | 20070228174 11/395569 |
Document ID | / |
Family ID | 38557372 |
Filed Date | 2007-10-04 |
United States Patent
Application |
20070228174 |
Kind Code |
A1 |
Vinogradov; Igor R. ; et
al. |
October 4, 2007 |
Imaging-based bar code reader utilizing stitching method and swipe
guide
Abstract
An imaging-based bar code reader that includes an item guide to
guide movement of an item including a target bar code such that
target bar code passes through a field of view of the reader in a
straight line. The reader further includes an imaging and decoding
system to: 1) capture a series of images which include at least a
part of the target bar code as the bar code is moved through the
field of view of the reader; 2) sequentially analyze the series of
captured images, for each captured image, identifying areas of the
captured image representative of an image of the target bar code
and decode decodable portions of the imaged target bar code; and 3)
combining the decoded portions of the imaged target bar code using
a sequence stitching method to obtain a full decode of the target
bar code.
Inventors: |
Vinogradov; Igor R.; (New
York, NY) ; Trajkovic; Miroslav; (Coram, NY) ;
Barkan; Edward; (Miller Place, NY) |
Correspondence
Address: |
TAROLLI, SUNDHEIM, COVELL & TUMMINO L.L.P.
1300 EAST NINTH STREET, SUITE 1700
CLEVEVLAND
OH
44114
US
|
Assignee: |
SYMBOL TECHNOLOGIES, INC.
Holtsville
NY
|
Family ID: |
38557372 |
Appl. No.: |
11/395569 |
Filed: |
March 31, 2006 |
Current U.S.
Class: |
235/462.43 ;
235/462.11; 235/462.41 |
Current CPC
Class: |
G06K 7/14 20130101 |
Class at
Publication: |
235/462.43 ;
235/462.41; 235/462.11 |
International
Class: |
G06K 7/10 20060101
G06K007/10 |
Claims
1. An imaging-based bar code reader for reading a target bar code
affixed to an item, the reader comprising: an imaging and decoding
system for imaging and decoding the target bar code, the imaging
and decoding system including focusing optics and a sensor array,
the focusing optics defining a field of view and focusing reflected
illumination from the target bar code onto the sensor array; an
item guide to guide movement of the item such that target bar code
passes through a field of view of the focusing optics in a straight
line; and wherein the imaging and decoding system: captures a
series of images which include at least a part of the target bar
code as the target bar code is moved through the field of view of
the focusing optics; sequentially analyzes the series of captured
images, for each captured image, identifying areas of the captured
image representative of an image of the target bar code and
decoding decodable portions of the imaged target bar code; and
combines the decoded portions of the imaged target bar code
obtained from the series of captured images to obtain a full decode
of the target bar code.
2. The bar code reader of claim 1 wherein the reader includes a
housing supporting the imaging and decoding system and the item
guide is affixed to the housing.
3. The bar code reader of claim 2 wherein the item guide includes a
pair of parallel rails to guide the item along a straight line path
of travel.
4. The bar code reader of claim 3 wherein the pair of parallel
rails include longitudinally extending slots which are sized to
receive respective end portions of the item to guide the item along
the straight line path of travel.
5. The bar code reader of claim 4 wherein the item guide further
includes a stop member bridging respective ends of the pair of
parallel rails to define an end of the straight line path of travel
of the item.
6. The bar code reader of claim 2 wherein the housing supports a
transparent window and reflected illumination from the target bar
code passes through the window and is received by the focusing
optics.
7. The bar code reader of claim 6 wherein a path of travel of the
target bar code is substantially parallel to an outer surface of
the window as the target bar code passes through the field of view
of the focusing optics.
8. The bar code reader of claim 1 wherein the sensor array of the
imaging and decoding system is a 2D sensor array.
9. The bar code reader of claim 1 wherein the imaging assembly
includes a camera assembly disposed within a camera assembly
housing, the camera assembly supporting the focusing optics and the
sensor array.
10. The bar code reader of claim 2 wherein the housing includes a
flat bottom portion adapted to be positioned on a counter to permit
hands-free operation of the reader.
11. The bar code reader of claim 1 further including an
illumination system to direct illumination along the field of view
of the focusing optics.
12. A method of reading a target bar code comprising: providing an
imaging and decoding system for imaging and decoding the target bar
code, the imaging and decoding system including focusing optics and
a sensor array, the focusing optics defining a field of view and
focusing reflected illumination from the target bar code onto the
sensor array; providing an item guide to guide movement of the item
such that target bar code passes through a field of view of the
focusing optics in a straight line; capturing a series of images
which include at least a part of the target bar code as the target
bar code is moved through the field of view of the focusing optics;
sequentially analyzing the series of captured images, for each
captured image, identify areas of the captured image representative
of an image of the target bar code and decoding decodable portions
of the imaged target bar code; and combining the decoded portions
of the imaged target bar code obtained from the series of captured
images to obtain a full decode of the target bar code.
13. The method of claim 12 wherein imaging and decoding system are
supported in a housing and the item guide is affixed to the
housing.
14. The method of claim 12 wherein the item guide includes a pair
of parallel rails to guide the item along a straight line path of
travel.
15. The method of claim 14 wherein the pair of parallel rails
include longitudinally extending slots which are sized to receive
respective end portions of the item to guide the item along the
straight line path of travel.
16. The method of claim 15 wherein the item guide further includes
a stop member bridging respective ends of the pair of parallel
rails to define an end of the straight line path of travel of the
item.
17. The method of claim 13 wherein the housing supports a
transparent window and reflected illumination from the target bar
code passes through the window and is received by the focusing
optics.
18. The method of claim 17 wherein a path of travel of the target
bar code is substantially parallel to an outer surface of the
window as the target bar code passes through the field of view of
the focusing optics.
19. The method of claim 12 wherein the sensor array of the imaging
and decoding system is a 2D sensor array.
20. The method of claim 12 wherein the focusing optics and the
sensor array are disposed within a camera assembly housing.
21. The method of claim 13 wherein the housing includes a flat
bottom portion adapted to be positioned on a counter.
Description
FIELD OF THE INVENTION
[0001] The present invention relates to an imaging-based bar code
reader and, more particularly, to a hands-free bar code reader that
facilitates reading of high density bar codes by utilizing an
sequence stitching method and by providing an item swipe guide to
provide straight line movement of the bar code as it moves though a
field of view of the reader.
BACKGROUND OF THE INVENTION
[0002] Various electro-optical systems have been developed for
reading optical indicia, such as bar codes. A bar code is a coded
pattern of graphical indicia comprised of a series of bars and
spaces having differing light reflecting characteristics. The
pattern of the bars and spaces encode information. In certain bar
codes, there is a single row of bars and spaces, typically of
varying widths. Such bar codes are referred to as one dimensional
(1D) bar codes. Other bar codes include multiple rows of bars and
spaces, each row typically having the same width. Such bar codes
are referred to as two dimensional (2D) bar codes and examples
include PDF417 and DataMatrix bar code formats. By virtue of the
use of multiple rows of features (bars and spaces), 2D bar codes
typically allow more encoded information than a 1D bar code in a
given bar code area. Devices that read and decode one and two
dimensional bar codes utilizing imaging systems that image and
decode imaged bar codes are typically referred to as imaging-based
bar code readers or bar code scanners.
[0003] Imaging systems include charge coupled device (CCD) arrays,
complementary metal oxide semiconductor (CMOS) arrays, or other
imaging pixel arrays having a plurality of photosensitive elements
or pixels. An illumination system comprising light emitting diodes
(LEDs) or other light source directs illumination toward a target
object, e.g., a target bar code. Light reflected from the target
bar code is focused through a lens of the imaging system onto the
pixel array. Thus, an image of a field of view of the focusing lens
is focused on the pixel array. Periodically, the pixels of the
array are sequentially read out generating an analog signal
representative of a captured image frame. The analog signal is
amplified by a gain factor and the amplified analog signal is
digitized by an analog-to-digital converter. Decoding circuitry of
the imaging system processes the digitized signals and attempts to
decode the imaged bar code.
[0004] A continuing trend is bar code technology is increasing
density of bar codes, that is, encoding more information in a given
bar code area. For many items, the available area where a bar code
may be imprinted is limited. Thus, if more information is desired
to be encoded in a bar code, bar code density must be increased,
hence the trend from 1D to 2D bar codes. Increasing the density of
a 2D bar code requires increasing the number of bar code features
(bars or stripes) in a given area. However, decreasing feature size
leads to problems in imaging resolution and decoding of high
density 2D bar codes, such at PDF 417 and DataMatrix bar codes
which utilize very small feature size.
[0005] What is desired is an imaging-based bar code reader that
provides for effective reading of high density 2D bar codes.
SUMMARY OF THE INVENTION
[0006] The present invention concerns an imaging-based bar code
reader that includes an item guide to guide movement of an item
including a target bar code such that target bar code passes
through a field of view of the reader in a straight line and
further including an imaging and decoding system to: 1) capture a
series of images which include at least a part of the target bar
code as the bar code is moved through the field of view of the
reader; 2) sequentially analyze the series of captured images, for
each captured image, identify areas of the captured image
representative of an image of the target bar code and decode
decodable portions of the imaged target bar code; and 3) utilize an
sequence combining or stitching method to combine the decoded
portions of the imaged target bar code to obtain a full decode of
the target bar code.
[0007] The item swipe guide that directs movement of the target bar
code through the reader field of view in a straight line path such
that relative positions of the imaged target bar code with respect
to captured images of the series of captured images are linearly
aligned along an axis corresponding to movement of the item with
respect to the item guide. The linear alignment of the imaged
target bar code positions within the series of captured images
enhances the capability of the imaging and decoding system to
identify and decode decodable portions of the imaged target bar
code.
[0008] These and other objects, advantages, and features of the
exemplary embodiment of the invention are described in detail in
conjunction with the accompanying drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
[0009] FIG. 1 is a schematic perspective view of an imaging-based
bar code reader of the present invention including an item swipe
guide;
[0010] FIG. 2 is a schematic perspective view of the imaging-based
bar code reader of FIG. 1 with the guide removed;
[0011] FIG. 3 is a schematic sectional view of a portion of the
imaging-based bar code reader of FIG. 1 showing the scanner
head;
[0012] FIG. 4 is a block circuit diagram of the imaging-based bar
code reader of FIG. 1;
[0013] FIG. 5A is an upper portion of a flow chart showing the
imaging and decoding process utilized by imaging and decoding
systems of the imaging-based bar code reader of FIG. 1; and
[0014] FIG. 5B is a lower portion of the flow chart of FIG. 5A.
DETAILED DESCRIPTION
[0015] An imaging-based reader, such as an imaging-based bar code
reader, is shown schematically at 10 in FIGS. 1-4. The bar code
reader 10 is capable of imaging and decoding both 1D and 2D bar
codes, such as a 2D bar code shown at 14, utilizing a sequence
stitching method, as explained below. Additionally, the reader 10
is also capable of capturing images and signatures. The bar code
reader 10 includes a housing 11 supporting an imaging system 10 and
a decoding system 40 within an interior region 11a of the housing
11. The housing 11 supports a transparent window 17 through which
reflected illumination from the target bar code 14 is received by
the imaging system 10.
[0016] The bar code reader 10 includes an imaging system 20 and a
decoding system 40. The imaging system 20, when enabled, during an
exposure period, captures an image frame 42 of a field of view FV
of the imaging system. During an imaging session to read a target
bar code 14, the imaging process is repeated to capture a series of
image frames 43 as the target bar code 14 is moved through the
imaging system field of view FV. Each of the series of captured
image frames 43 includes at least a portion of an image 14' of the
target bar code. The decoding system 40 sequentially analyzes each
image frame 42 of the series of image frames 43 and attempts to
decode decodable portions of the imaged bar code 14'. The decoded
portions 14a' of the imaged bar code 14' are stored in a buffer
memory 44a.
[0017] Utilizing a sequence stitching method, each time a decoded
portion 14a' is stored in the buffer memory 44a, the decoding
system 40 attempts to combine or stitch the decoded portions 14a'
stored in buffer memory to achieve a full decode of the target bar
code 14. The sequential analysis, partial decoding and stitching of
decoded portions of the imaged bar code 14' continues until a full
decode of the target bar code 14 is achieved. Further, the reader
10 of the present invention includes an item guide 80 which directs
movement of an item 15 to which the target bar code 14 is affixed
such that the target bar code moves through the field of view FV
along a linear travel path.
[0018] The reader 10 has enhanced capability of successfully
reading high density 2D bar codes where successful reading is
limited by PPM (pixels per module) constraints. PPM is a measure of
how many active pixels of a sensor array the smallest feature (bar
or stripe) of a bar code is imaged onto. For a given sized sensor
array, the higher the density of a bar code, the lower the PPM and
as PPM decreases the capability of the imaging system to obtain an
image that permits complete decoding of the bar code also
decreases. By obtaining partial decodes of the imaged bar code 14
appearing in successive capture images 43 and then combining those
partial decodes until a full decode is achieved, the reader 10 of
the present invention overcomes the need for obtaining a single
image that allows a full decoding and thereby enjoys enhanced high
density reading capability.
[0019] This high density reading capability of the reader 10 is
further enhanced by the item guide 80 which, as will be explained
below, provides that a relative position of the image 14' of the
target bar code 14' within each of the series of captured images 43
is linearly aligned with respect to each other and parallel with an
axis of movement G defined by the item guide 80, that is, the axis
corresponding to a path of travel PT of the item 15 in or on the
guide 80. The linear alignment of the position of the imaged target
bar code 14' leads to more robust and efficient decoding of the
imaged target bar code 14'.
[0020] The imaging system 20 comprises and an imaging camera
assembly 22 and associated imaging circuitry 24. The imaging camera
22 includes a housing 25 supporting focusing optics including a
focusing lens 26 and a 2D photosensor or pixel array 28. The
imaging camera 22 is enabled during an imaging session to capture a
sequence of images of the field of view FV of the focusing lens 26.
A subset of the sequence of captured images will define the series
of images 42 that include a full or partial image 14' of the target
bar code 14. Since only captured images that include at least a
portion of an image of the target bar code 14 are useful for
decoding the target bar code, captured images not including any
portion of the target bar code are ignored.
[0021] In one preferred embodiment of the present invention, the
bar code reader 10 is a hands-free reader including a generally
upright housing 11 having a flat base portion 11b that is adapted
to be placed on a counter or tabletop wherein an operator presents
the target bar code 14 imprinted on an item or object 15 to the
reader 10 for reading, that is, imaging and decoding the target bar
code 14. For example, the item 15 may be a driver's license having
a 2D bar code 14 imprinted on a surface 15a of the item 15.
Preferably, the target bar code 14 is imaged by moving or swiping
the surface 15a of the item 15 through the field of view FV of the
focusing lens 26 utilizing the item guide 80.
[0022] As is best seen in FIG. 3, the bar code reader housing 11
defines the interior area 11a. Disposed within the interior area
11a is bar code reader circuitry 13 including the imaging and
decoding systems 20, 40 and an illumination assembly 60 which, when
enabled, directs illumination through the transparent window 17 and
onto the target bar code 14. The bar code reader circuitry 13 is
electrically coupled to a power supply 16, which may be in the form
of an on-board battery or a connected off-board power supply. If
powered by an on-board battery, the reader 10 may be a stand-alone,
portable unit. If powered by an off-board power supply, the reader
10 may have some or all of the reader's functionality provided by a
connected host device.
[0023] Circuitry associated with the imaging and decoding systems
20, 40, including the imaging circuitry 24, may be embodied in
hardware, software, firmware, electrical circuitry or any
combination thereof and may be disposed within, partially within,
or external to the camera assembly housing 25. The imaging camera
housing 25 is supported with an upper or scanning head portion 11c
of the housing and receives reflected illumination from the target
bar code 14 through the transparent window 17 supported by the
scanning head 11c. The focusing lens 26 is supported by a lens
holder 26a. The camera housing 25 defines a front opening 25a that
supports and seals against the lens holder 26a so that the only
illumination incident upon the sensor array 28 is illumination
passing through the focusing lens 26.
[0024] Depending on the specifics of the camera assembly 22, the
lens holder 26a may slide in and out within the camera housing
front opening 25a to allow dual focusing under the control of the
imaging circuitry 24 or the lens holder 26a may be fixed with
respect to the camera housing 25 in a fixed focus camera assembly.
The lens holder 26a is typically made of metal. A back end of the
housing 25 may be comprised of a printed circuit board 25b, which
forms part of the imaging circuitry 24 and may extend beyond the
housing 25 to support the illumination system 60.
[0025] The imaging system 20 includes the sensor array 28 which may
comprise a charged coupled device (CCD), a complementary metal
oxide semiconductor (CMOS), or other imaging pixel array, operating
under the control of the imaging circuitry 24. In one exemplary
embodiment, the pixel array 28 comprises a two dimensional (2D)
mega pixel array with a typical size of the pixel array being on
the order of 1280.times.1024 pixels. The pixel array 28 is secured
to the printed circuit board 25b, in parallel direction for
stability.
[0026] As is best seen in FIG. 3, the focusing lens 26 focuses
light reflected from the target bar code 14 through an aperture 26b
onto the pixel/photosensor array 28. Thus, the focusing lens 26
focuses an image of the target bar code 14 (assuming it is within
the field of view FV) onto the array of pixels comprising the pixel
array 28. The focusing lens 26 field of view FV includes both a
horizontal and a vertical field of view, the vertical field of view
being shown schematically as FVV in FIG. 3.
[0027] During an imaging session, multiple images of the field of
view FV of the reader 10 are obtained by the imaging system 20. An
imaging session may be instituted by an operator, for example,
pressing a trigger to institute an imaging session prior to swiping
the item 15 through the guide 80. Alternately, the imaging system
20 may institute an imaging session when a lower or bottom edge 15b
of the item 15 begin moving through an upper portion of the field
of view FV. Yet another alternative is to have the imaging system
30 always operational such that image after image is captured and
analyzed for the presence of at least a part or portion of an
imaged target bar code 14'. In any event, the process of capturing
an image 42 of the field of view FV during an imaging session will
be explained in general terms. Electrical signals are generated by
reading out of some or all of the pixels of the pixel array 28
after an exposure period. After the exposure time has elapsed, some
or all of the pixels of pixel array 28 are successively read out,
thereby generating an analog signal 46 (FIG. 4). In some sensors,
particularly CMOS sensors, all pixels of the pixel array 28 are not
exposed at the same time, thus, reading out of some pixels may
coincide in time with an exposure period for some other pixels.
[0028] The analog image signal 46 represents a sequence of
photosensor voltage values, the magnitude of each value
representing an intensity of the reflected light received by a
photosensor/pixel during an exposure period. The analog signal 46
is amplified by a gain factor, generating an amplified analog
signal 48. The imaging circuitry 24 further includes an
analog-to-digital (A/D) converter 50. The amplified analog signal
48 is digitized by the A/D converter 50 generating a digitized
signal 52. The digitized signal 52 comprises a sequence of digital
gray scale values 53 typically ranging from 0-255 (for an eight bit
processor, i.e., 2.sup.8=256), where a 0 gray scale value would
represent an absence of any reflected light received by a pixel
(characterized as low pixel brightness) and a 255 gray scale value
would represent a very intense level of reflected light received by
a pixel during an integration period (characterized as high pixel
brightness).
[0029] The digitized gray scale values 53 of the digitized signal
52 are stored in the memory 44. The digital values 53 corresponding
to a read out of the pixel array 28 constitute the image frame 42,
which is representative of the image projected by the focusing lens
26 onto the pixel array 28 during an exposure period. If the field
of view FV of the focusing lens 26 includes the target bar code 14,
then a digital gray scale value image 14' of the target bar code 14
would be present in the image frame 42.
[0030] The decoding circuitry 40 then operates on the digitized
gray scale values 53 of the image frame 42 and attempts to decode
any decodable part or portion of that image frame 42 that is
representative of a part or portion the imaged target bar code 14'.
The decoded portions 14a' of the imaged target bar code' are stored
in the buffer memory 44a.
[0031] Obviously, if a single image frame 42 includes a decodable
portion that is representative of or corresponds to the entire
imaged target bar code 14' and thereby allows complete decoding of
the target bar code in one image frame 42, the decode is complete
and a signal for successful decode is generated to activate the
speaker 59a and/or LED indicator 59b to let the operator know that
decoding of the target bar code 14 has been completed. However with
high density bar codes, this will rarely occur because of PPM
limitations. Thus, a series of images 43 will need to be obtained,
analyzed and partial decodes combined or stitched together
utilizing a stitching method to achieve a complete decode.
[0032] If the decoding is successful, decoded data 56,
representative of the data/information coded in the bar code 14 is
then output via a data output port 57 and/or displayed to a user of
the reader 10 via a display 58. Upon achieving a good "read" of the
bar code 14, that is, the bar code 14 was successfully imaged and
decoded, a speaker 59a and/or an indicator LED 59b is activated by
the bar code reader circuitry 13 to indicate to the user that the
target bar code 14 has successfully read, that is, the target bar
code 14 has been successfully imaged and the imaged bar code 14'
has been successfully decoded.
[0033] The bar code reader 10 further includes the illumination
assembly 60 for directing illumination to illuminate the target bar
code 14 along the field of view FV. The illumination assembly 60
and the aiming apparatus 70 operate under the control of the
imaging circuitry 24. In one preferred embodiment, the illumination
assembly 60 is a single LED 62 producing a wide illumination angle
to completely illuminate the target bar code 14.
[0034] The LED 62 is supported within the scanning head 11b just
behind the transparent window 17 and face forwardly, that is,
toward the target bar code 14. The LED 62 is positioned away from
the focusing lens 26 to increase the illumination angle (shown
schematically as I in FIG. 3) produced by the LED 62. Preferably,
the illumination provided by the illumination assembly 60 is
intermittent or flash illumination as opposed to continuously on
illumination to save on power consumption. Also, preferably, the
LED 62 is red at the higher end of the red wavelength range, e.g.,
approximate wavelength around 670 nanometers (nm.)), since red LEDs
of this wavelength have been found to provide for efficient
conversion of electrons to photons by the LEDs and from photons
back to electrons by the photosensor array 28.
Imaging and Decoding Process Utilizing Stitching Method and Item
Guide
[0035] FIG. 1 illustrates one exemplary embodiment of the guide 80
of the present invention. The guide 80 includes body 81 defining a
pair of vertically opposing walls 92. The opposing walls 92 define
a pair of inwardly-facing, parallel, vertical side rails 82. Formed
in each side rail 82 is a slot 84 that extends a length of
respective rail. The slots 84 are substantially parallel to an
outer surface 17a of the transparent window 17. Positioned at a
downward end of the side rails 82 is a lower stop 86 which bridges
the side rails 82. The item guide 80 forces the item 15, when
inserted into the slots 84, to be moved along the linear path of
travel PT which corresponds to the axis G of the guide and which is
parallel the transparent window outer surface 17a. The guide 80
defines a large central opening 87 which is aligned with the window
17 so the item 15 is visible to the window 17 when the item 15 is
inserted into the slots 84.
[0036] The guide 80 may be affixed to the housing 11 or be a
stand-alone component placed in proximity to the housing 11. If
affixed to the housing 11, the body 81 may be permanently or
releasably affixed to the housing. In the exemplary embodiment
shown in FIGS. 1 and 2, the guide body 81 is affixed to the front
surface 11d of the upper portion 11c of the housing 11. The front
surface 11d of the housing includes two extending arms 11e. The
distal ends of the arms 11e slideably engage respective slots 88 in
outer surfaces 90 of the opposing vertical walls 92 of the body 81
to secure the body 81 to the housing 11. The body 81 rests on an
outward step 11f of the upper portion 11c of the housing 11.
[0037] With the bar code reader circuitry 13 energized, the item 15
such that the surface 15a faces the transparent window 17 and the
opposite ends 15b of the item 15 are aligned with the parallel
slots 84. The item 15 is then swiped or moved downwardly along the
path of travel PT such that the target bar code 14 passes in a
straight line through the field of view FV of the reader 10. The
item 15 is moved downwardly within the slots 84 until a lower edge
15c of the item 15 bottoms out on the lower stop 86 of the guide
80. After contacting the lower stop 86, the item 15 is raised
upwardly along the path of travel PT, again being constrained by
the parallel slots 84 of the rails 82 until the lower edge 15a of
the item 15 clears the rails 82.
[0038] During the time the item 15 is inserted, lowered, raised and
removed with respect to the guide 80, the imaging system 20
captures a successive series of images 42 as the item is moved or
swiped through the field of view FV of the reader 10. Since the
target bar code 14 is imprinted on the item surface 15a, at least
some of the successive images will include parts or all of the
target bar code 14 as the bar code passes through the field of view
FV. These images are referred to as the series of captured images
43. Captured images 42 that do not include at least a portion of
the imaged target bar code 14' are of no interest and are
discarded.
[0039] Further, since the target bar code 14 moves in a straight
line with respect to the field of view FV, a relative position of
the imaged target bar code 14' in each image 42 of the series of
images 43 will be linearly aligned with respect to each other and
parallel to the movement axis G of the guide 80. This alignment
enables the imaged bar code 14' to be more easily located in each
image 42 of the series of captured images 43 and facilitates the
decoding process since it makes it easier for the decoder system 40
to use a sequence stitching method to properly piece or stitch
together a number of partial decodes to obtain a full decode of the
target bar code image 14'. Further the side rails 82 are aligned to
be substantially parallel to the outer surface 17a of the window
17, the target bar code 14 moves in a plane that is substantially
parallel to the window at a distance from the focusing lens 26 that
provides for a sharp focusing of the target bar code 14 onto the
sensor array 28 as the target bar code passes through the field of
view FV.
[0040] The steps of the imaging and decoding process are show
generally at 100 in the flow chart of FIG. 5. A reading session is
commenced to read the target bar code 14 at 105. At step 110,
utilizing the imaging system 10, an image frame 42 is captured by
reading out the pixel array 28 after an exposure time to generate
the analog signal 46 and the analog signal is digitized and digital
gray scale values 53 are generated and stored in memory 44. This
process continuously repeats during the entirety of the imaging
session storing a sequence of captured images in the memory 44.
[0041] At step 120, after the gray scale values 53 of an image
frame 42 are stored in memory 44, the decoding system 40 analyzes
or operates on the gray scale values 53 to see if any portion of an
imaged bar code 14' is present in the image frame 42. If at step
120, the captured image frame 42 analyzed by the decoding system 40
is not found to include any portion of an imaged bar code, at step
125, the image frame is discarded and the process loops back to
step 120 wherein the next captured image frame 42 in the sequence
of captured image frames is selected and the analysis of step 120
is repeated.
[0042] If at step 120, the image frame 42 is found to contain a
portion or the entirety of an imaged bar code 14', then, at step
130, the decoding system 40 attempts to decode the imaged bar code
14' or portion of imaged bar code 14' (represented by the gray
scale values 53).
[0043] If at step 135, the attempted decoding of the imaged bar
code 14' or portion of the imaged bar code 14' is determined to be
completely unsuccessful, the process loops back to step 125 and
then to step 120 wherein the next captured image frame 42 stored in
memory 42 is selected and analyzed. If at step 135, the attempted
decoding of the imaged bar code 14' is determined to result in a
complete, successful decoding of the imaged target bar code 14' in
its entirety, then the process is complete and, at step 140, a
signal representing a successful read is generated to alert the
operator via the speaker 59a and/or the LED indicator 59b. Also,
the buffer memory 44a is cleared.
[0044] If, at step 135, the attempted decoding of the imaged bar
code 14' is determined to be partially successful and a partial
decoding of the imaged bar code 14' is achieved, then at step 150,
the partial decode 14a' is stored in the buffer memory 44a. Then,
at step 160, the buffer memory 44a is operated on by the decoder
system 40 to determine if there are any previous partial decodes
14a' of the imaged target bar code 14' stored in buffer memory 44a.
If no other partial decodes 14a' are found, then the process
returns to step 125 and then to step 120 wherein the next captured
image frame 42 is selected and analyzed.
[0045] If one or more partial decodes are found, then at step 170,
all of the partial decodes 14a' found in the buffer memory 44a are
operated on sought to be combined utilizing a sequence stitching
method to see if a successful, complete decode of the imaged bar
code 14' can be achieved. At step 180, if a complete decode cannot
be achieved, then the process returns to steps 125 and then 120
wherein the next captured image frame 42 in memory 44 is selected.
If, at step 180, combining the partial decodes results in a
successful, complete decode of the imaged bar code 14', then the
process is complete and the process transfers to step 140 where a
signal representing a successful read is generated to alert the
operator via the speaker 59a and/or indicator LED 59b that a good
read has been achieved.
[0046] A bar code sequence stitching method utilizing a buffer
memory is disclosed in U.S. Pat. No. 5,821,519, which issued on
Oct. 13, 1998 to Lee and Spitz and which is assigned to the
assignee of the present invention. The '519 patent is incorporated
herein in its entirety by reference. Another reference disclosing
sequence stitching methodologies is a book entitled Algorithms on
Strings, Trees, and Sequences: Computer Science and Computational
Biology, by Dan Gusfield, published by the Press Syndicate of the
University of Cambridge, Cambridge, England, copyright 1997, ISBN
0-521-58519-8 (hc). The aforementioned book is incorporated herein
in its entirety by reference.
[0047] One exemplary item guide 80 is shown in FIG. 1 which is
especially suitable for small, thin cards, such as driver's
licenses, credit cards, identification cards, etc. However, it
should be appreciated that depending on the configuration of the
item 15 and configuration and position of the target bar code 14
with respect to the item, a wide variety of guides may be utilized
as would be understood by one of skill in the art, e.g., a pair of
spaced apart L-shaped frames which a box-like item 15 can be slid
along, a slit in a structure through which an item 15 is passed,
etc. It is the intent of the present invention to cover all such
item guides.
[0048] While the present invention has been described with a degree
of particularity, it is the intent that the invention includes all
modifications and alterations from the disclosed design falling
within the spirit or scope of the appended claims.
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